Although it is common knowledge that warmth is a vitally necessary ingredient in the care and treatment of animals, particularly, but not limited to, small animals such as dogs or cats, there are few if any commercially available, safe and convenient devices for this purpose. Typical of the patented devices are the heated pet beds of R. D. Huffman shown in U.S. Pat. Nos. 2,980,058 and 3,125,663. These devices are primarily support pads containing electrical heating elements for the comfort and protection of the animal. These and similar devices are mere variations of the obvious use under the animal of an electric heating pad similar to those used by humans. There are two major disadvantages to such devices which render them unsuitable for widespread use. The most obvious problem is that of the danger of the electricity to the animals. It must be assumed that any animal, even if sick or otherwise enfeebled, will chew or claw anything in its immediate environs. Electric pad controls and wiring are dangerous for the animals' normally harmless chewing which could result in electrocution or fire. Many devices, such as the referenced Hoffman devices, have been designed to minimize the danger.
The second more subtle, problem with devices using electrically heated pads to support the animal is the likelihood of producing a hot spot or localized area of increased heat. This is the same problem recognized with electric blankets and heating pads for humans and has resulted in the required warning that such devices should not be used with young children, enfeebled elderly persons or anyone unconscious, immobilized or otherwise incapable of protecting themselves from such problems. This problem, heretofore unsolved for apparatus for pets, has severely limited the use of electric heating pads for animals.
One known device intended for use in providing heat and support for animals is the "T PUMP" and "T PAD" system distributed by Graymar Industries, Inc. of Buffalo, N.Y., which, from published literature appears to be a flat flexible pad having conduits for circulating water and a water pump connected thereto by means of soft flexible hoses. The separate pump includes a heating mechanism of some type which serves to elevate the temperature of water in the pump which is then circulated to the pad. The complexity, cost and vulnerability to damage by the animal limit the widespread use of this device.
Additionally, as the owners of water beds for humans often discover, water beds such as the design by Charles P. Hall shown in U.S. Pat. No. 3,585,356 attract the household pets. Such human water beds are not suitable, however, for convenient use in the care of animals because the thin, flexible vinyl bladder may easily be punctured by tooth or claw with disastrous results. In addition to the obvious size problems, the motion of a flexible water support which humans find so comforting is usually unacceptable to an animal. Further, such water beds cannot be used for the very young animals such as a prematurely born kitten or puppy that could easily fall off the pad or simply crawl away losing the benefits of the warmth.